WordStream has recently published a list of the most expensive Adwords keywords as of July 2011.

97% of Google's revenue comes from Adwords or advertising on blogs and websites. Just to give you an idea of how much Google earns from this program, during the last four quarters (that's from Q3 2010 to Q2 2011), the company's total advertising revenue amounted to a whopping $32.2 billion!

Here are some of the keywords in 20 categories that proved to be true money-makers for Google:

Notice that the most expensive keyword categories represent businesses with high lifetime customer value (e.g. lawsuits, server applications) – as these industries can afford to pay a lot to acquire a new customer.

What does this list mean to Adsense Publishers?

Well, if you're the type of Publisher who just wants to make a lot of money from writing, it would make sense to publish articles about these high-paying keywords. Then again, remember that competition is extremely tight in these categories -- and if money is your only motivation or if you're not passionate at all about these topics, you might lose your interest in writing way before you actually make money from it.

What does this list mean to Online Marketers?

If your industry falls in any of these categories, at least, you'd know what to expect should you want to launch an online ad campaign. Remember that there are various techniques that you can use to compete in a high-volume, high Cost per Click category - such as being more target specific, optimizing landing pages and using negative keywords, among others - to get the most out of your investment.